1. Field of the Invention
The invention concerns anti-tartar dental compositions based on zinc citrate which have improved taste.
2. The Related Art
Tartar, known also as calculus, is a hard mineralized deposit which forms around teeth. This formation arises from deposition of crystals of calcium phosphate in the pellicle and the extracellular matrix of dental plaque. Various forms of calcium phosphate have been identified but the most difficult to remove and thermodynamically most stable form is called hydroxyapatite (HAP). Amorphous forms of calcium phosphate are believed to be the precursors of HAP. Regular brushing can usually remove the amorphous forms but is not fully effective to dislodge the final stable calculus form. Therefore it is desirable to prevent amorphous forms of calcium phosphate from transforming into HAP. The art has recognized that agents which interfere with the formation of HAP crystallization will be effective anti-tartar agents.
Zinc citrate has for many years been formulated into commercial dentifrices as an anti-tartar agent. Not only does it interfere with HAP crystallization, but it also has anti-bacterial activity. In the United Sates, zinc citrate has been formulated into toothpastes marketed under the Mentadent(copyright), Close-Up(copyright) and Aim(copyright) brands sold by the Unilever operating companies. The technology is described in disclosures such as U.S. Pat. No. 4,022,880 (Vinson et al.), U.S. Pat. No. 4,647,452 (Ritchey et al.) and U.S. Pat. No. 5,372,803 (Williams et al.).
A major drawback of zinc citrate formulations is that the zinc ion imparts a relatively bitter taste. Smokers are particularly sensitive to the adverse taste.
Accordingly, it is an object of the present invention to provide an oral composition formulated with a zinc anti-tartar salt characterized by an improved taste.
These and other objects of the present invention will become more apparent in light of the detailed description and Examples which follow.
An oral product is provided comprising:
(i) from about 0.001% to about 20% of beads which include a zinc salt having an average particle size ranging from about 0.01 to about 5 mm; and
(ii) a dental base.
Now it has been found that the bitter taste of zinc salts can be improved by incorporating the zinc salt in the form of relatively large active beads. On an equal zinc salt weight basis, the beads are at least as effective in anti-tartar activity as solubilized or dispersed non-complexed zinc salts of the known art.
Zinc salts usable for the present invention may include inorganic or organic counterions. Organic counterions include C2-C20 compounds, especially carboxylates. Preferred organic counterions include citrates, malates, malonates, maleates, adipates, succinates, acetates, propionates, lactates, tartrates, glycolates and combinations thereof. Most especially preferred is zinc citrate trihydrate.
Inorganic zinc salts are less preferred than the organic ones. These include counterions such as halides (e.g. chloride, bromide and iodide), sulfates, nitrates, phosphates and combinations thereof.
Amount of the beads may range from about 0.01 to about 20%, preferably from about 0.5 to about 10%, optimally from about 1 to about 5% by weight of the total oral product.
Optionally, a gum may be incorporated into the beads of the present invention. Illustrative gums are polysaccharides including sodium carboxymethyl cellulose (CMC), hydroxyethylcellulose, methylcellulose, ethylcellulose, hydroxypropyl cellulose, hydroxypropyl methylcellulose, gum tragacanth, gum arabic, gum karaya, pectin, carageenan, guar, xanthan gum, starch and combinations thereof. Most preferred are the cellulose type gums, especially sodium carboxymethyl cellulose (CMC). All molecular weight types of sodium CMC may be useful, although the medium viscosity grade such as the 9M grade is most suitable.
Beads of the present invention normally will contain essentially only zinc citrate. In a less preferred but useful embodiment, the beads may be formed by the complexion of the zinc salt with a gum in the presence of water to form gel particles. Relative weight ratios of the zinc salt to gum in this embodiment, may range from about 10,000:1 to about 10:1, preferably from about 1,000:1 to about 100:1 by weight.
In some embodiments of the present invention, water may be present within the beads. In those situations, the relative weight ratios of the zinc salt to water in the beads may range from about 50:1 to about 1:50, preferably from about 20:1 to about 1:1, optimally from about 10:1 to about 6:1 by weight.
Typically the amount of zinc salt in the beads is about 100%. However, in some embodiments the amount of zinc salt in the beads may range from about 15 to about 99%, sometimes from about 50 to about 95%, but optimally from about 90 to 100% by weight of the beads. When a gum is present, amounts of the gum within the bead may range from about 0.001 to about 2%, preferably from about 0.1 to about 1%, optimally from about 0.25 to about 0.5% by weight of the beads. The remainder of the bead composition generally is water present in amounts from about 1 to about 60%, preferably from about 2 to about 40%, optimally from about 5 to about 20% by weight of the beads.
Average particle size of the beads and also of the zinc salt may range from about 0.01 to about 5 mm, preferably from about 0.05 to about 3 mm, optimally from about 0.1 to about 2 mm. Bulk density of the beads may range from about 0.75 to about 0.95, preferably from 0.80 to 0.90, optimally from 0.81 to 0.84 gm/cc.
Beads according to the present invention are prepared prior to introduction into a dental base with other ingredients of the oral product. Zinc salt and any optional ingredients such as gum and water can be formed by mixing in a Hobart type blending apparatus.
In one embodiment, the beads are visually distinct in the dental base. This may be accomplished by the beads being opaque and the base being transparent. Alternatively, the beads may appear as clear bodies colored differently from a transparent or opaque base.
Besides the beads, the oral product will contain a dental base in an amount of about 80 to about 99% by weight. Ingredients of the dental base may include humectants, thickeners, abrasives, anti-caries agents, surfactants, colorants, flavorants, opacifiers, water and a variety of special actives (e.g. desensitization agents such as potassium nitrate, peroxides and anti-bacterials such as triclosan).
Surfactants useful herein may be of the anionic, nonionic, cationic, zwitterionic or amphoteric type. Most preferred are sodium lauryl sulphate, sodium dodecylbenzene sulfonate and sodium lauryl sarcosinate. Amounts of the surfactant may range from about 0.5 to about 10%, preferably from about 1 to about 5% by weight of the dental base.
Humectants useful herein are usually polyols. Illustrative of this category are sorbitol, maltitol, mannitol, glycerin, propylene glycol, xylitol, hydrogenated corn syrup, polyethylene glycols and mixtures thereof. Amounts of the humectant may range from about 1 to about 60%, preferably from about 5 to about 50%, optimally from about 10 to about 40% by weight of the dental base.
Thickeners useful herein may be the same gums as utilized to complex with the zinc salts. However, these gums will be formulated into the dental base rather than into the pre-formed beads. Illustrative thickeners include sodium carboxymethyl cellulose, ethylcellulose, carageenan, xanthan gum, pectin, chemically modified starches and acrylates. The latter may be crosslinked polyacrylates such as Carbopol(copyright) 934. Inorganic thickeners are exemplified by silica aerogels and magnesium aluminum silicate, commercially available as Veegum(copyright). Amounts of the thickener may range from about 0.01 to about 30%, preferably from about 0.1 to about 20%, optimally from about 0.5 to about 5% by weight of the dental base.
A fluoride anti-caries compound normally is usually present as part of the dental base. Illustrative of such fluoride compounds are sodium fluoride, potassium fluoride, calcium fluoride, stannous fluoride, stannous monofluorophosphate, sodium monofluorophosphate and copper fluoride. Most preferred is sodium fluoride. These sources should release anywhere from about 25 to about 5,000 ppm of fluoride ion. The anti-caries compound will normally be present in an amount from about 0.01 to about 5%, preferably from about 0.1 to about 2.5%, optimally from about 0.2 to about 1.5% by weight of the dental base.
Abrasives may also be present in the dental base. Illustrative materials include sodium metaphosphate, dicalcium phosphate, calcium pyrophosphate, silica, alumina, chalk, insoluble bicarbonate salts and mixtures thereof. Amounts of the abrasive may range from about 1 to about 80%, preferably from about 5 to about 50% by weight of the dental base.
When the oral compositions are gels, structurants may be necessary. Particularly useful as a structurant are potyoxyethylene-polyoxypropylene copolymers such as those sold under the trademark Pluronic(copyright). These materials are also known as Potoxamers and employed in amounts from about 5 to about 30%, preferably from about 18 to about 25% by weight of the dental base.
Flavors may also be part of the dental base. These flavors may be based on oils of spearmint and peppermint. Examples of other flavoring materials include menthol, clove, wintergreen, eucalyptus and aniseed. Flavors may range in amount from about 0.1 to about 5% by weight of the dental base.
Sweetening agents may also be included in the dental base. Illustrative agents include saccharin, sodium cyclamate, aspartame, acesulfame, xylitol and combinations thereof at levels from about 0.1 to about 10% by weight of the dental base.
Other additives may also be incorporated into the dental base. These may be anti-tartar agents, colorants, preservatives, silicones, other synthetic or natural polymers such as Gantrez 597(copyright), and mixtures thereof. Amounts of these other ingredients may range from about 0.01 to about 20% by weight of the dental base.
Water may be present in the dental base in amounts from about 1 to about 95%, preferably from about 10 to about 60%, optimally from about 20 to about 50% by weight of the dental base.
Except in the operating and comparative examples, or where otherwise explicitly indicated, all numbers in this description indicating amounts of material ought to be understood as modified by the word xe2x80x9caboutxe2x80x9d.
The term xe2x80x9ccomprisingxe2x80x9d is meant not to be limiting to any subsequently stated elements but rather to encompass non-specified elements of major or minor functional importance. In other words the listed steps, elements or options need not be exhaustive. Whenever the words xe2x80x9cincludingxe2x80x9d or xe2x80x9chavingxe2x80x9d are used, these terms are meant to be equivalent to xe2x80x9ccomprisingxe2x80x9d as defined above.
The following examples will more fully illustrate the embodiments of this invention. All parts, percentages and proportions referred to herein and in the appended claims are by weight unless otherwise illustrated.